Problem: When parents bring their children in for shots, I often sense a touch of gratitude that their own time at the mercy of the needle has passed. Wrong. Many adults are due for shots. Their doctors often neglect this, but the recently issued U.S. Recommended Adult Immunization Schedule should remind them.

Question: Why immunize adults? The answer is simple: It's the most natural, specific, and cost-effective way of preventing illness. Vaccines take advantage of the body's ability to act as a chemical factory. Exposed to a protein from a virus or to a fragment extracted from a bacterial cell, our body recognizes the material as something resembling an invading parasite, and makes a protein molecule (an antibody) to stop the invader. Since the person who was vaccinated is prevented from getting the infection, he or she also can't pass it on, and thus helps break the chain of infection (an advantage called "herd immunity").

Recommendations: With time, sometimes the protection children receive through immunization fades and needs a boost. What are the vaccines recommended for adults?

• The newly introduced Tdap. This boosts protection against diphtheria, whooping cough, and lockjaw, a horrible illness caused by certain soil bacteria when they enter the body through a deep injury (think of stepping on a rusty nail). The vaccine should be repeated every 10 years and should also be given after an injury if it's been more than five years since your last dose.

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• Two doses of chickenpox vaccine and (if you were born after 1957) at least one dose of measles, mumps, or rubella vaccine. If you are 60 years or older, the shingles vaccine is strongly recommended. None of these should be given to pregnant women or people with suppressed immune systems.

• If you are a woman under 27, three doses of the HPV vaccine against cervical cancer and genital warts.

• If you are older than 50 or live in a household with a child under 2, an annual flu shot.

• If you are traveling to a wonderful place with less than wonderful sanitation, seek out a hepatitis A shot—nothing spoils a vacation like vomiting, diarrhea, and turning yellow.

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Conclusion: You may need to press your doctor about immunizations, since thinking about vaccines doesn't come as naturally to internists as to pediatricians, and some dislike the special storage requirements and expense that vaccines entail. But do press—you and everybody around you will be healthier for it.

Problem: I'm a skeptic about the value of cough medicine for kids. Still, I've been spending an inordinate amount of time this season seeing unhappy, coughing children and placating their parents, who are distressed by the FDA's warning against over-the-counter cough and cold remedies for children under the age of 2.

New research: Happily, the wonders of modern science (aided by a grant from the National Honey Board) have come to my rescue. A new study demonstrates the value of an alternative that's cheaper, safer, and tastier: buckwheat honey. The researchers studied its effectiveness by randomly dividing a group of about 100 children with colds into three groups. One group was given honey before going to bed at night. Another group was given a syrup containing dextromethorphan, or DM, a common cough suppressant, colored and flavored to resemble honey. The third group was given nothing at all.

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Findings: The next day, the parents were surveyed about the effects on their children's coughing and sleep. The honey was somewhat more effective than the DM cough syrup for each of the outcomes measured (the differences were consistent, though not statistically significant). Both were better than nothing at all. Surprisingly, in this study some side effects (like hyperactivity, nervousness, and insomnia) were seen more often in the children taking honey than in the children treated with the DM syrup, though side effects are one of the main reasons that DM products have been prohibited or discouraged. The difference, however, is that DM's side effects, though quite rare, can sometimes be very serious, which we doubt is true of honey.

Caveat: Because of a rare but very dangerous risk to infants given honey of contracting botulism, the sweetener should never be given to children less than 1 year old.

Conclusion: Why might honey help soothe a cough? We don't know. But it's certainly an established folk remedy. My mother, for instance, was a strong believer, especially when she added butter to the mix. (For adults, she recommended whiskey and lemon juice.) Because honey is at least as good as, and perhaps better than, now-prohibited conventional cough syrup, I again have a way to fend off children's coughs and parents' helplessness. Great!

Question: What happens when seemingly sound medical advice turns out to be wrong or obsolete?

New research: Three physicians in Greece at the University of Ioannina School of Medicine became curious about this question. They looked at a number of cases in which an early study, widely read and quoted by doctors as the basis for strong recommendations to patients, turned out to be incorrect. The original studies were observational—large numbers of people were surveyed, and the results were analyzed for associations between a suspected cause and an anticipated outcome. The later studies that debunked the earlier results were randomized patient trials.

Example: The first studies testing the role that vitamin E, an antioxidant, was believed to play in preventing heart disease tracked the diets and hearts of 90,000 middle-aged nurses over eight years. The researchers corrected for other obvious factors, like smoking, and found that, as they had suspected might be the case, women who took vitamin E for an extended time had a substantially lower likelihood of developing heart disease. The authors were careful to say that their study only described an association, but a huge number of doctors took the question as settled and recommended vitamin E supplements (I took them myself). Then the results of some large randomized trials came out. Patients had been randomly assigned to take vitamin E or something that looked similar—and the findings showed that vitamin E seemed to increase the risk of heart disease slightly.

Findings: At that point, I stopped taking vitamin E. But did doctors who write for medical journals stop approvingly citing the old studies? Nope. To be sure, there was something of a drop-off in references to the original incorrect paper, but hardly a dramatic one. Four years after the initial findings were definitely disproved, fully half the new articles still described the old research results positively.

Conclusion: It appears that our conclusions, once accepted, are very hard to kill off—and this might be particularly true for plausible-seeming ideas. Somehow, doctors have to figure out how to give up on such notions when they turn out to be incorrect. For that to happen, both doctors and patients need to remember that scientific knowledge is not immutable, and doctors not infallible.

Sydney Spiesel is a pediatrician in Woodbridge, Conn., and clinical professor of pediatrics at Yale University's School of Medicine.